1. Field of the Invention
This invention relates to an Interline CCD (hereinafter IT-CCD) and a manufacturing method thereof and in particular to an IT-CCD and a manufacturing method thereof. Especially, the invention relates to an IT-CCD intended for miniaturization and high quality of an inter-electrode insulation film of charge transfer electrodes of a single-layer structure.
2. Description of the Related Art
An IT-CCD used with an area sensor, etc., has charge transfer electrodes for transferring signal charges from a photoelectric conversion section. The charge transfer electrodes are placed contiguously on a charge transfer passage formed on a semiconductor substrate and driven in order.
The IT-CCD having charge transfer electrodes involves the following problem: With the advance of miniaturization according to the demand for increasing the number of photograph pixels, the area in which incidence light from a slanting direction can be gathered lessens and the sensitivity is degraded. Thus, it is required that any area other than a photoelectric conversion section be thinned as much as possible. Since a light shield film needs to be formed in any area other than the photoelectric conversion section, preferably the area is flattened as much as possible.
Thus, an IT-CCD having single-layer wiring electrodes with charge transfer electrodes placed without being superposed is proposed. The IT-CCD has an inter-electrode insulation film between contiguous charge transfer electrodes, and a silicon-based conductive material such as polycrystalline silicon is used as the material of the charge transfer electrodes.
On the other hand, the IT-CCD requires high-speed transfer of signal charges with upsizing and an increase in the number of pixels. To drive a charge transfer electrode of a single-layer structure with a high-speed pulse, the distance (gap) from the contiguous charge transfer electrode needs to be formed narrow (0.1 μm or less). High withstand voltage is required for insulation between electrodes.
To provide such an electrode pattern, for example, an EB direct drawing method is used on a flat surface; an expensive stepper needs to be used. Even if an electrode pattern can be provided, it is extremely difficult to fill a minute inter-electrode area with an insulating film, also causing withstand voltage to be lowered; it is practically impossible.
It is therefore an object of the invention to provide a power-thrifty IT-CCD having a charge transfer electrode area thinned for improving the light reception efficiency of a photoelectric conversion section and being capable of executing high-speed and high-sensitivity transfer without lowering withstand voltage between charge transfer electrodes. It is another object of the invention to provide a manufacturing method of an easily manufactured and highly reliable IT-CCD.